Helicopter drip pan

ABSTRACT

A drip pan apparatus for a “M” model BLACK HAWK® helicopter and the like includes an expanded corner structure for accommodating an access port also positioned further outwardly in the corner than in prior drip pan apparatuses, facilitating filter viewing while retaining peripheral o-ring seal. An expanded corner of the airframe skirt is accommodated by the expanded corresponding corner of a frame, which also defines a small radius internal curve. The removable pan has a small radius curve cooperating with the small radius curve of the frame and is sealed thereto by the peripheral o-ring seal sealing the entire pan to the frame. Physical access to the filter is enhanced.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the filing benefit of U.S. ProvisionalApplication No. 61/014,960, filed Dec. 19, 2007, the disclosure of whichis incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

This invention relates to a fluid-tight drip pan, and more specificallyto a fluid-tight drip pan for the engine or transmission compartment ofa helicopter.

BACKGROUND OF THE INVENTION

Larger helicopters, in general, have several features in common in atypical basic configuration or layout. For instance, a typicalhelicopter will have a cabin section rearward of the pilot's cockpit orflight deck and which is used to transport people, cargo or both. Inaddition, the helicopter will have an engine compartment which islocated typically above and to the rear of the pilot's cockpit or flightdeck, and above the cabin section. The engine compartment typicallyhouses two primary components, at least one engine and a rotortransmission with a corresponding transmission housing.

Both the engine and the rotor transmission contain numerous fluids, suchas petroleum-based lubricants, that are critical to the operation of theengine and the transmission. These fluids inevitably leak from variouslocations in the engine and the transmission during both the operationand storage of the helicopter. Because the engine compartment isgenerally oriented above the cabin section, any leaking fluidseventually seep or drip into the cabin section, unless proper sealingmechanisms are in place. The inflow of these leaking fluids spoil, stainor damage the cabin's interior materials such as seat covers andacoustic linings. In addition, the leaking fluids can severely damage ordestroy sensitive electronic equipment that may be placed in the cabinsection of a helicopter.

Moreover, the exterior of the helicopter around the engine andtransmission compartment is not completely fluidtight, allowing fluidsuch as water to leak from these areas into the cabin with similaradverse effects.

During routine inspection and maintenance it is necessary to have bothready visual and physical access to portions of the engine or at leastthe rotor transmission. Such access is required to check critical fluidlevels, to replace worn, damaged or depleted parts or filters, or toadjust mechanical systems. Typically, various access panels in or aroundthe engine or transmission compartments provide the requisite openingsto achieve ready access to the engine and the rotor transmission. Insome helicopters, a forged or fixed airframe structure forms an accessopening which is located below the rotor transmission housing and abovethe cabin section. The opening is thus accessible through the cabin'sceiling. This access opening, however, must be sealed by a cover againstthe inevitable oil and fluid drippings which the engine and the rotortransmission will produce, as well as against water leakage.

The access opening below the engine compartment in the priorhelicopters, such as the BLACK HAWK® helicopter, made for the UnitedStates by Sikorsky Aircraft Company of Stratford, Conn., is defined byboth the aircraft structural forgings and a flexible or yieldabledownwardly-turned skirt which is riveted onto the helicopter's forgedstructure. The skirt is thin and many times more flexible relative tothe helicopter's forged structure.

Prior drip pan designs attached a covering plate directly to theflexible skirt with a hollow seal sandwiched therebetween. One hollowseal used in prior designs resembled the flexible, hollow door sealsused around car doors or refrigerator doors. However, the skirt containssurface aberrations, such as the protruding rivet heads from the rivetssecuring the skirt to the forged helicopter structure. When the sealengaged both the skirt and the rivet heads, it could be upset enough sothat leakage occurred. Accordingly, the hollow seal traversing theseaberrations while sandwiched between the skirt and the covering plate isunable to provide a suitable, consistent, long-term fluid seal.Moreover, flexing of the flexible skirt could also cause leakage.

Also, the geometry of the cover cannot be such that it protrudessignificantly into the interior of the cabin section. Headroom in thecabin section typically is limited and any additional protrusion fromthe ceiling of the cabin section is undesirable. In addition, becauseweight is critical to the operation of any aircraft, heavy coverconstructions are undesirable.

Other prior drip pan structures disclosed in U.S. Pat. Nos. 6,112,856;6,216,823; 6,446,907 and Design U.S. Pat. No. D444,443, which are fullyincorporated herein by this express reference, provided improvements andsolutions to these difficulties. However, Sikorsky has now introducedits “M” Model BLACK HAWK® helicopter for which these prior structuresare not readily adaptable due to a change in configuration of the skirtnoted above.

In particular, while the prior drip pans provided a port for visualaccess to an oil filter, the port was offset from the filter, renderingit more difficult to see the filter from many viewing angles through theport, also requiring specially shaped tools to manipulate filterretention bolts and requiring tilting of filters when removed orreplaced.

The “M” model is currently in the process of introduction by Sikorskyfor use by U.S. Military. In that model, and in other aircraft with whatare or will be similarly-shaped skirts, there is still a skirt asdisclosed in the prior U.S. Pat. No. 6,446,907 with the exception thatin the access area or corner for the filter, the corner of the skirt hasbeen pulled outwardly to allow direct and straight-through access to thefilter and its filter retention bolts where the pan is removed. Suchdirect access is preferable as it eliminates the need for the specialdog-bone shaped tools necessary to operate the filter retention bolts toremove and install the filter as was required with the prior drip pan,which not only required such tools but also required the filter to be“tipped” as it was removed or replaced and before it could be seated(see FIG. 6 of U.S. Pat. No. 6,446,907). Accordingly, in the new “M”model, one corner of the old prior skirt has been pulled or extendedoutwardly and asymmetrically to the other corners.

Stated in another way, the radius point or center of the expanded cornercurve of the skirt has been moved outwardly from its position in theprior drip pan and the straight sides of the skirt are no longer tangentto the curve of this corner.

Such modification of the skirt renders the prior symmetric frame anddrip pan incompatible with the new “M” model air frame. There is orwould be a gap between the new skirt at the expanded corner and the olddrip pan and drip pan frame. Accordingly, there is no way for the olddrip pan and frame structure of the prior patents, including U.S. Pat.No. 6,446,907, to provide sealing for the new “opened” corner defined bythe new skirt to allow more direct access to the filter.

In order to overcome this problem, the old frame and drip pan could bere-shaped to the new skirt shape, however, the requirement to seal thepan peripherally to the frame in such a case would require extensive andexpensive re-working of the peripheral seal structure of the pan. Inparticular, the pan would require a special seal seat groove to bemilled or otherwise manufactured into the edge of the pan.

Specifically, since the straight skirt sides extend in a directionintersecting with, and are no longer tangent to, the skirt curve at thiscorner, the skirt takes on inwardly-facing convex shapes, directedinwardly of the access opening, before flowing into the new expandedinwardly-facing concave corner. This skirt configuration would require acooperative configuration of the drip pan whose cover would follow thatof the skirt. When a drip pan for a corresponding frame is so shaped,the peripheral o-ring sealing the drip pan to the frame cannot be usedas with the prior o-ring groove due to the changed configuration of thesealing surfaces. When stretched to fit, the o-ring on the drip panwould not follow this curved portion of the pan because it would spanacross the corresponding outwardly-facing concave drip pan curves. Thus,the fit of the o-ring would render installation of the pan to the frameproblematical and adversely affect the desired seal.

In other words, the spanning o-ring would interfere with thecorresponding inwardly-facing convex curve of the frame when the pan wasinserted therein. This would, in turn, require the provision of a muchmore expensive and complicated o-ring retaining groove in the peripheraledge of the removable pan.

Moreover, the aforesaid problem of visual access to the filter throughthe corresponding site port has remained a problem. It is desired toenhance the location of the port to facilitate more visual access to thefilter and to its “bypass button” from more viewing locations. Theretention of the prior site port in its same position relative to theold drip pan, however, would retain the visual disadvantages mentioned.

Accordingly, it is one objective to provide an improved leak-proof drippan apparatus for use in “M” model BLACK HAWK® helicopters.

A further objective of this invention is to provide an improved coverand seal for the interior access opening of helicopters such as theBLACK HAWK® “M” model helicopter and those of similar structure.

Another object of this invention is to provide a drip pan that willeffectively and consistently seal fluid from passage from an engine ortransmission compartment to a cabin section of a BLACK HAWK® “M” modelhelicopter and similar air frames.

Another object of this invention is to provide a drip pan which permitsquick visual and physical access to the engine or transmissioncompartment of a BLACK HAWK® “M” model helicopters and similarhelicopters without requiring modification to the existing aircraftstructure.

Another objective of the invention is to more effectively seal a drippan to the skirt defining a transmission access opening in a BLACK HAWK®“M” model helicopters and similar helicopters.

Still another object of this invention is to provide a drip pan that canbe attached to the existing structure of a BLACK HAWK® “M” modelhelicopter and similar helicopters without modification of the existingairframe structure and with minimal intrusion into the helicopter'scabin section.

Another objective of the invention is to provide an improved drip panfor use with BLACK HAWK® “M” model helicopter and similar air framesusing an o-ring seal between drip pan and frame, where all peripheralcurves in the pan are convex (i.e., outwardly directed) with respect tothe pan.

Yet another objective of the invention is to provide enhanced visualaccess to a filter in an “M” model BLACK HAWK® helicopter.

SUMMARY OF THE INVENTION

In other features and functions, the new helicopter drip pan apparatusherein covers and effectively seals a structural opening in thehelicopter without leakage.

To these ends, in one embodiment, a drip pan is adapted to cooperatewith a frame having an inwardly-facing peripheral surface. The frame issecured to a depending skirt which defines the structural access openingfor access to a rotor transmission of a BLACK HAWK® Model “M”helicopter. The access opening also provides access to components, suchas an oil filter, attached to the rotor transmission.

The drip pan comprises a substantially planar member defining an accessport and having an outwardly-facing peripheral surface. The access portpermits access to the oil filter and the outwardly-facing peripheralsurface defines a first pan corner and a plurality of other corners. Theoutwardly-facing peripheral surface adapted to cooperate with theinwardly-facing peripheral surface of the frame. The first pan corner isasymmetric in curvature to the other corners such that the substantiallyplanar member is adapted to be removably received within the frame in asingle orientation. The pan further comprises a removable port coveradapted to be removably received within said access port.

Another embodiment of the invention herein contemplates a re-shapedframe with a modified filter access corner which has an outwardlyexpanded, asymmetric corner shape corresponding generally to match thenew skirt corner configuration of the “M” model BLACK HAWK® helicopter.Also, the frame has a corner structure forming an inside extension atthis corner which is contoured or shaped to define a relatively smallradius internal concave corner defining a sealing surface for thecorresponding small radius corner of the pan which corner is asymmetricin curvature to the other three corners of the pan. The smaller radiusof the pan corner allows a filter access port to be moved slightlyoutwardly, toward the corner, so it can be aligned with the filterthereabove. The filter access port, therefore, facilitates visual accessto the filter while the small radius corner of the pan provides enhancedphysical access to the filter.

This configuration is attained despite and contrary to the previouslyconventional wisdom than an o-ring seal could not be used effectivelyabout and around the relatively small radius of the pan corner.According to conventional wisdom, placing the o-ring seal about such asmall radius would result in undue stretch of the o-ring. The belief wasthat the resulting reduction in diameter of the o-ring would, in turn,result in seal efficiency derogation or other seal failure. Contrary tothis belief, embodiments of the pan apparatus do not result in astretched o-ring and, furthermore, do not require the o-ring to fit intoany concave areas extending into the pan to avoid an otherwiseinterference fit between the o-ring and frame upon pan insertion.

In yet another embodiment, the frame comprises a first straight side, asecond straight side, and a corner structure connecting the firststraight side and the second straight side. The first straight side, thesecond straight side, and the corner structure collectively define aninwardly-facing peripheral surface which cooperates with anoutwardly-facing peripheral surface of the pan. The corner structuredefines a relatively small radius external concave corner and has atleast one width that is greater than the width of the first straightside. In another embodiment, the corner structure has at least one widththat is greater than the width of the second straight side.

These and other objectives and advantages will become readily apparentfrom the following description of embodiments of the invention and fromthe drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-6 are reproduced herein from the prior U.S. Pat. No. 6,446,907for clarity of contrast to the present invention and are described inthat patent;

FIG. 7 is an exploded isometric view of components of the new drip panapparatus according to one embodiment of the invention;

FIG. 8 is a plan view of the drip pan of FIG. 7 as will be viewed fromthe cabin section of a helicopter when in use;

FIG. 9 is an enlarged view of the new corner structure according to oneembodiment of the invention in the upper left-hand corner of FIG. 8 butillustrating the prior art access port in phantom for comparison;

FIG. 9A is a cross-sectional view of the corner structure in FIG. 9, butillustrating the prior art skirt in phantom for comparison;

FIG. 9B graphically illustrates the new frame of the apparatuscontrasted with the old skirt and old pan corner orientation;

FIG. 10 is a cross-sectional view taken along lines 10-10 of FIG. 8;

FIG. 11 is an exploded cross-sectional view similar to FIG. 10 butshowing the port cover removed and illustrating the replacement of afilter through the port; and

FIG. 12 is an isometric view of the new drip pan (with port covers notshown for clarity) from the perspective of the transmission side of thenew drip pan when in use.

PRIOR ART

Applicant first describes the prior art as in U.S. Pat. No. 6,446,907for purposes of environment background and contrast with the invention.Item numbers shown in FIGS. 2-6 when used on FIGS. 7-12 designatecomponents in FIGS. 7-12 which are similar or identical to components inFIGS. 2-6.

FIG. 1 shows a widely known configuration of a typical helicopter 10.While the typical helicopter 10, for example, in this prior descriptionwas a BLACK HAWK® helicopter as manufactured for the United States bySikorsky Aircraft Company, Stratford, Conn., it will be appreciated thatthe drip pan structure described in the prior patents was useful innumerous aircraft and helicopter configurations of other prior makes andmodels. In this configuration the helicopter 10 had a cabin 12 (dashedoutline) in which passengers, equipment and cargo could ride duringoperation. Located just above the cabin 12 was at least one engine 14which supplied power to a rotor transmission 16. The rotor transmission16 was connected to a shaft 18 which imparted rotary motion to the mainrotor 20. The rotor transmission 16 was also connected via a drive shaft(not shown) to a tail rotor 22.

The rotor transmission 16 required frequent inspection and maintenanceto ensure proper operation of the transmission. To facilitate easy andready access to the rotor transmission, rotor transmission accessopenings were provided on both the exterior and interior of thehelicopter. For example, structural opening 24 was located within thecabin 12, providing the requisite access to the rotor transmission 16situated directly above the cabin 12. Structural opening 24 generallyhad some type of removable covering to seal the transmission area 16from the cabin area 12. To accommodate attachment of a removablecovering, a flexible skirt 26 (FIG. 2) was fixedly secured around theperiphery of structural opening 24 by rivets 28. Skirt 26 was many timesmore flexible than the structural opening 24 to which it attached.

As can be further appreciated the rotor transmission 16 as well as theengine 14 required various fluids during their respective operations.Generally, these fluids provided the rotor transmission 16 and theengine 14 with lubrication, cooling, and the like. During operationthese fluids may leak and drip from either the engine 14 or rotortransmission 16 or both. To prevent leakage of fluid into the cabin 12via structural opening 24, a drip pan apparatus 30, as shown in FIG. 2,was used to cover and seal the structural opening 24.

With specific reference to FIGS. 2-6, the drip pan apparatus 30according to one preferred embodiment of the prior structure had a framemember 32, a drip pan 34, and a seal member 36 cooperating together toprovide a fluid tight sealing arrangement for structural opening 24.Frame member 32 had a plurality of lugs 38 disposed about the exteriorperiphery of frame member 32. Four lugs 38 were disposed on two sides ofthe frame member 32 and three lugs 38 were disposed on the other twosides of the frame member 32. Fasteners 40 cooperated with lugs 38 andthreaded retention members 42 (FIG. 4) to secure frame member 32 toskirt 26 attached to structural opening 24. Once installed, frame member32 typically remained in place and was not routinely removed fromstructural opening 24, although it could be readily removed by simplyextracting fasteners 40. Frame member 32 was many times more rigid thanthe flexible skirt 26.

Drip pan 34 had a plurality of resilient members 50 which serve to holddrip pan 34 in sealing engagement with frame member 32. Each resilientmember 50 had elongated arms 52 with curved portions 54. Resilientmembers 50 were free to pivot about brackets 58. Curved portions 54selectively engaged slots 56 opening toward and located about theinterior periphery of frame member 32. To secure drip pan 34 to framemember 32, the drip pan 34 was pushed into the interior of frame member32 until the drip pan 34 contacted lip 60 (FIG. 4) which extended aroundframe member 32 and acted as a stop for drip pan 34. Only part of thecurved portions 54 were resiliently inserted into slots 56. Theinstallation and the removal of the drip pan 34 was accomplished ratherquickly using the resilient members 50 because no tools such asscrewdrivers or wrenches were required. Equally important, resilientmembers 50 were permanently secured to the drip pan 34 by brackets 58,so the resilient members 50 could not be lost or misplaced when the drippan 34 was removed to gain full access to the engine 14 and rotortransmission 16.

As shown in FIG. 4, seal member 36 was disposed in an outwardly-facinggroove 62 which extended around the outer periphery of drip pan 34. Inthat application, the term “outwardly-facing” represents a directionsubstantially parallel to the plane of the drip pan 34 and extendingaway from the drip pan 34. As illustrated in FIG. 2, the outer peripheryof drip pan 34, which had four straight edges or sides 35 a, 35 b, 35 c,35 d connected by curved portions 37 a, 37 b, 37 c, 37 d, conformed toframe member 32 which was comprised of four straight sides or rails 39a, 39 b, 39 c, 39 d connected by curved portions 41 a, 41 b, 41 c, 41 d(shown in FIG. 3). With reference to FIGS. 5 and 6, when drip pan 34 wasinstalled into frame member 32, seal member 36 sealingly engagedinwardly-facing surface 64 of frame member 32 to achieve a fluid tightsealing arrangement between drip pan 34 and the frame member 32. In thisapplication, the term “inwardly-facing” represented a directionsubstantially parallel to the plane of the frame member 32 and extendingtoward the interior of the frame member 32 and the pan 34. Unexpectedly,seal member 36 provided the necessary sealing engagement betweenoutwardly-facing seal member 36 and inwardly-facing surface 64 despitethe fact that groove 62 and surface 64 respectively ran along straightsides 35 a, 35 b, 35 c, 35 d and 39 a, 39 b, 39 c, 39 d. Typically,peripheral o-ring seals were used in cooperation with annular or curvedsealing surfaces such as those defined by curved portions 37 a, 37 b, 37c, 37 d and 41 a, 41 b, 41 c, 41 d (shown best in FIGS. 2 and 3). It waspreviously felt that peripheral seals used along straight sealingsurfaces would provide unacceptable sealing integrity.

In one prior drip pan design, a seal was located in a groove openingextending in a direction perpendicular to the plane of the drip pan. Theseal would engage a surface which was parallel to the plane of the dippan. With this arrangement, flexure of the helicopter frame associatedwith structural opening 24 may breach the seal integrity between thedrip pan and the attachment frame causing fluid to leak into thehelicopter cabin. Seal member 36 of these FIGS. 2-6, however, was aperipheral seal located in outwardly-facing groove 62 to form a fluidseal between the periphery of the drip pan 34 and the inwardly-facingsurface 64 of frame member 32. With this arrangement, flexure of thehelicopter frame associated with structural opening 24 did not breachthe integrity of the sealing arrangement between the drip pan 34 and theframe member 32. While the sealing member 36 could be any suitablecross-sectional geometry, seal member 36 was preferably an O-ring.

Routine maintenance and inspection of the rotor transmission 16, doesnot ordinarily require removal of the entire drip pan 34. As shown inFIG. 2, to accommodate limited access for routine maintenance orinspection, or filter replacement, a plurality of small, removableaccess port covers 70 were provided in drip pan 34 to allow accessthrough access openings or ports 72 to mechanical linkages in and aroundthe rotor transmission and to allow inspection of the fluid levelsassociated with the rotor transmission 16. An access cover 70 for eachaccess opening 72 was removably disposed in sealing engagement coveringthe access opening 72. To secure access cover 70 to the access opening72 in drip pan 34, each access cover 70 had a resilient member 74 whichfunctioned much like resilient member 54 which secured the drip pan 34to the frame member 32.

With reference particularly to FIGS. 5 and 6, access opening 72 had anannular groove 76 for resiliently receiving curved portion 78 ofresilient member 74 to sealingly secure access cover 70 to accessopening 72. Advantageously, no tools were required to operate theresilient members 74 to install or remove the access covers 70. Inaddition, brackets 80 permanently secured resilient member 74 to accesscovers 70 so resilient members 74 could not be lost or misplaced. Eachaccess cover 70 was attached to the drip pan 32 by a suitable attachmentdevice such as a cable or chain 82 so when an inspection procedure wascomplete the access cover 70 was readily retrieved and positioned intoaccess opening 72. Each access cover 70 included a seal member 84disposed in an annular groove 86 extending around the outer periphery ofaccess cover 70. When access cover 70 was placed into access opening 72,seal member 84 sealing engaged surface 88 of drip pan 34 which formedpart of access opening 72. Like seal member 36, seal member 84 formed aperipheral seal between the access cover 70 and the surface 88. Thisarrangement improved on prior sealing arrangements which located theseal member between an access cover surface parallel to but outside ofthe plane of the access cover 70 and the drip pan 32, i.e., a face seal.As discussed above, the peripheral seal arrangement provided improvedseal integrity even if the drip pan 34 flexed. Preferably, seal member84 was an O-ring.

To facilitate the removal of accessing covers 70 from access openings72, pull handles 90 were attached to access covers 70. Fasteners 92fixedly secured pull handles 90 to access covers 70. Preferably, pullhandles 90 were cable or chain.

During the preflight procedure of a helicopter, critical filters must bechecked and determined operational before the helicopter is allowed tofly. To facilitate this inspection process, at least one of the accessor port covers 70 had a transparent cover member 94 (FIG. 5) so that abypass button or valve associated with a particular filter could bechecked visually through the access cover 70 without physically removingthe access cover 70 from the access opening or port 72. A seal member 96was disposed between the transparent cover member 94 and access cover 70to prevent fluid leakage therebetween. Preferably, the transparent covermember 94 was made from acrylic such as Plexiglass™.

With reference to FIGS. 2-4, drip pan 34 had a drain hole 100 to drainfluid collected by the drip pan 34. Drain hole 100 included strainermembers 102 (shown in FIG. 4) to keep foreign objects coming to rest onthe drip pan 34 from clogging the drain hole 100. A drain tube 104 wasattached to the drain hole 100 to direct the collected fluid to a catchbasin (not shown) or to the exterior of the helicopter. The drain tube104 was made preferably from metal tubing having a diameter of about0.625 inches. Alternatively, a removable stopper could have been usedwith drain hole 100 for selective drainage.

In at least one application, as depicted in FIGS. 3 and 4, the drip panapparatus 30 could have been used on helicopters having carrousel barsadded to the interior of the helicopter cabin 12 (shown in FIG. 1) tosupport, for example, litters used for transporting patients in need ofmedical attention. Typically, at least one carrousel bar passed directlyunder the drip pan apparatus 34. To accommodate a carrousel bar 108(phantom), elongated recesses 110 were provided in frame member 32 sothat the frame member 32 did not interfere with the installation andoperation of the carrousel bar 108.

In still another application, the drip pan apparatus 30, and morespecifically the frame member 32, could have interfered with access toan oil filter associated with the rotor transmission 16 when the drippan apparatus 30 is installed. To provide for removal of an oil filter112 (FIG. 6) from the rotor transmission 16, a portion of frame member32 was machined away as shown by numeral 114 so that the oil filter 112could be removed along a line not perpendicular to the drip panapparatus 30. During the removal or installation of oil filter 112, thedrip pan 34 was removed to provide even greater access to the oil filter112. Frame member 34 was machined just enough to permit removal of oilfilter 112, and maintain sealing engagement between seal member 36 andsurface 64 of frame member 34.

To provide further access to the oil filter 112, the geometry of framemember 32 could be modified. More specifically and with reference toFIG. 3, frame member 32 was comprised of four straight sides or rails 39a, 39 b, 39 c, 39 d connected by curved portions 41 a, 41 b, 41 c, 41 d,where each rail 39 a, 39 b, 39 c, 39 d had a respective width indicatedby W₁, W₂, W₃, W₄. To provide improved access to the oil filter 112(shown in FIG. 6), the opening defined by rails 39 a, 39 b, 39 c, 39 dwas shifted to the left in FIG. 3 such that the respective widths W₁,W₂, W₃, W₄ of rails 39 a, 39 b, 39 c, 39 d were not all equal to oneanother. Preferably, the difference between W₂ and W₄ was about onequarter of an inch. This transverse shift of the opening helped toaccommodate removal of the oil filter 112 which was generally located inthe compartment above the drip pan apparatus 30 near the upper left handcorner of the drip pan apparatus 30 shown in FIG. 3.

Accordingly, the prior art disclosed above provided an improved coverand seal for the interior access opening of a helicopter such as theprior BLACK HAWK® helicopter models. As such, that drip pan apparatussealed against fluid passage from the engine or transmission compartmentto the cabin section of a prior model BLACK HAWK® helicopter. Inaddition, that drip pan apparatus permitted quick access to the engineor transmission compartment of that helicopter, without requiringmodification to the existing aircraft structure.

The new invention described below provides the same features andadvantages in a model “M” BLACK HAWK® helicopter, but also accommodatesthe new relieved skirt version of the new “M” model, providing moredirect filter access, while still providing the desirable seal functionsnoted above.

DETAILED DESCRIPTION OF INVENTION

Embodiments of the invention described herein differ from that prior artof U.S. Pat. No. 6,446,907 (the '907 patent) in the structure of theelements defining the asymmetric corner components of a drip panapparatus 200 shown in FIGS. 7-12. In other aspects, such as inmaterials of construction and function, in one embodiment, the drip panapparatus 200 of this invention is like that described in said patent.Accordingly, any item numbers found in FIGS. 7-12 which are the same asthose in FIGS. 2-6 designate like components. Moreover, the helicopter10 of FIG. 1 is similar in outward appearance to the “M” model BLACKHAWK® helicopter and for that reason is used herein to illustrate anoverall helicopter environment in which the new drip pan apparatus 200of FIGS. 7-12 is used.

Turning to FIG. 1, there is shown therein a helicopter 10 representinggenerally for this invention a BLACK HAWK® Model “M” helicopter of thetype made by the Sikorsky Aircraft Company of Stratford, Conn., andother helicopter air frames similar thereto. Like the prior BLACK HAWK®helicopter, the BLACK HAWK® “M” model helicopter has a cabin 12 and anengine or turbine 14 which powers a rotor transmission 16. Shaft 18transmits rotary motion to a rotor 20 while the transmission 16 is alsoconnected by a drive element (not shown) to tail rotor 22. Like theBLACK HAWK® helicopter, the BLACK HAWK® Model “M” helicopter has a fixedtransmission access opening but designated 205 in FIG. 1. The “M” modelembodies a variety of other differences from the prior BLACK HAWK®helicopter of FIG. 1 of the '907 patent but in ways not relevant to thisinvention except as further described.

Turning now to FIG. 7, the drip pan apparatus 200 has application foruse in a “M” model BLACK HAWK® helicopter and other similar airframeshaving the fixed transmission access opening 205 defined by an air framemember 206 and a depending flexible skirt 207 attached thereto. Skirt207, like skirt 26 of FIG. 2, is many times more flexible than air framemember 206 to which skirt 207 is attached. Skirt 207 of the BLACK HAWK®Model “M” helicopter has two straight portions 208, 209 and an expandedcorner 210 therebetween, as well as a remaining periphery defined bystraight sections and corners. Note that skirt 207, between straightportions 208, 209, forms two inwardly-facing convex curves 231, 232 andan inwardly-facing concave curve 230. The concave curve 230 is orientedinwardly at the corner 210 so that straight portions 208, 209 flow intothe curves 231, 232 which are tangent to, or flow into, curve 230. Itwill be appreciated that an extension of each straight portion 208, 209would intersect an extension of curve 230 at an angle greater than zerodegrees. In this manner, the corner 210 of skirt 207 has been expandedoutwardly of the location of the same corner of the prior skirt of the'907 patent.

In one embodiment of this invention, corner 210 is asymmetric to theother corners (not shown) of the skirt 207, which other corners mayremain in the same configuration. In other words, the corner 210 isdefined by a shape that is different than the other corners of the skirt207. By contrast, in the access opening covered by the prior drip pansof the '907 patent all four corners of the prior skirt were symmetrical.As is described below, the drip pan apparatus 200 sealingly cooperateswith the skirt 207, including the corner 210, to cover access opening205 to prevent fluid drippings from entering the cabin 12 of the Model“M” BLACK HAWK® helicopter 10.

To that end, and with continued reference to FIG. 7, the drip panapparatus 200 includes a frame 215 having a corner structure 216, a drippan 220 having a new corner 221, and an o-ring seal 222. In use, theframe 215 is secured to air frame member 206. As shown, rivets 201 orother fasteners may secure the frame 215 to the skirt 207 and air frame206 through tabs 202. A flexible sealing media (not shown), such asPROSEAL™ (manufactured by PRC Desoto International, Inc. ofIndianapolis, Ind., a PPG Company) or other sealant may be used to sealthe frame 215 to skirt 207 when the frame 215 is secured to the airframe 206.

Thereafter, drip pan 220 is inserted into the frame 215 in the positionillustrated in FIGS. 7 and 8, where seal member or o-ring 222 creates aperipheral seal between the drip pan 220 and frame 215 and providescontinuous sealing during air frame flexure and without the disadvantageof any face seal in this regard. Attachment members 50 releasably securethe drip pan 220 to the frame 215 similarly to the prior pan of the '907patent where elongated arm 52 with curved portions 54 selectively engageslots 56. Once the pan 220 is inserted into the frame 215, a drain line104 may be connected to pass drainage fluids from drain 100.

As set forth above, and with continued reference to FIG. 7, the frame215 accommodates the outward expansion of the skirt 207 at corner 210.In particular, as is described in more detail below, corner structure216 of frame 215 has been expanded outwardly to match the outwardexpansion of the skirt 207, as shown. In addition, the radius of theinwardly-facing frame corner represented at 242 has been significantlyreduced to correspond to a relatively small radius of corner 221 of drippan 220.

With reference to FIGS. 7 and 8, the frame 215 comprises four straightsides or rails 247 a, 247 b, 247 c, 247 d connected by curved portions249 a and 249 b, the corner structure 216, and curved portion 249 c,respectively. The rails 247 a, 247 b, 247 c, 247 d; the curved portions249 a, 249 b, 249 c; and the corner structure 216 collectively definethe inwardly-facing peripheral surface 235 (shown in FIG. 7). Each rail247 a, 247 b, 247 c, 247 d has a respective width indicated by W₅, W₆,W₇, W₈ (labeled in FIG. 8) measured from the inwardly-facing peripheralsurface 235 to an outer periphery of the frame 215.

In one embodiment and with reference to FIG. 7, the width of the cornerstructure 216 varies to accommodate the expansion of the skirt 207,specifically the curve 230, at corner 210. The variation in the width ofthe corner structure 216 is shown in FIGS. 8 and 9A. As shown, the widthof the corner structure 216 transitions from the width W₇ of rail 247 cto width W₈ of rail 247 d. In one embodiment, at least a portion of thecorner structure 216 is wider than either adjacent rail 247 c or rail247 d. Specifically, the width of the corner structure 216 at onelocation, for example at width W₉ or width W₁₁ may be greater thaneither width W₇ or width W₈. By way of further example, as depicted inFIGS. 8 and 9A, the width of corner structure 216 may transition fromwidth W₇ to width W₉ that is greater than width W₇. The width of thecorner structure 216 then decreases from width W₉ into aninwardly-facing frame corner 242 or width W₁₀ that is less than thewidth W₉. Further, the width of the corner structure 216 then increasesto width W₁₁ before transitioning to a narrower width W₈ of rail 247 d.It will be appreciated that the width of the corner structure 216 mayvary smoothly from W₇ to W₈.

Furthermore, to provide improved access to the filter F (shown in FIG.11), the opening defined by rails 247 a, 247 b, 247 c, 247 d may beshifted to the left in FIG. 8 such that the respective width W₆ andwidth W₈ of rails 247 b and 247 d are not equal to one another. Thistransverse shift of the opening helps to accommodate removal of thefilter which is generally located in the compartment above the drip panapparatus 200. It will be appreciated that widths W₅, W₆, W₇, W₈ may notbe equal to any of the widths W₁, W₂, W₃, W₄ of FIG. 3.

With regard to the pan 220 and with further reference to FIG. 7, the pan220 has an outwardly-facing peripheral surface 239, which has fourstraight sides 250 a, 250 b, 250 c, 250 d connected by corners 211, 212,213, and corner 221. The outwardly-facing peripheral surface 239conforms to the inwardly-facing peripheral surface 235. As set forthabove, the radius of the corner 242 is significantly reduced tocorrespond to the radius of the corner 221 of the pan 220. As shown inFIGS. 7 and 8, the corner 221 is developed about a much smaller radiusthan its other pan corners 211-213. It will be appreciated that thevariation of the radius configuration of the corner 221 from the corners211-213 simplifies installation of the pan 220 by preventing incorrectinstallation since the pan 220 may be inserted into the frame 215 inonly one orientation.

Additionally, in one embodiment, the drip pan 220 defines a plurality ofaccess ports 223-226 and a filter access port 228, which is providedwith a removable port cover 229 having a view window 236 and frame 237.Once the drip pan 220 is secured to the frame 215, the status of afilter or other component in or on the transmission may be viewedthrough the view window 236. Also, any one or more of the access covers70 may be removed from its respective access port 223-226 such thatroutine maintenance and inspection of components within access opening205 may be performed. In one embodiment, the drip pan apparatus 200differs from that pan apparatus of the prior '907 patent only in thearea A as identified in FIG. 8.

FIGS. 9, 9A, and 9B illustrate area A of FIG. 8 in greater detail. Asshown in FIG. 9, the extra material provided by expansion of the pan 220out to the smaller radius corner 221 allows port 228 to be moved outtoward the corner 221 and more directly under (when in use) a filtercompared to the prior art port 72 (shown in phantom line). Thuspositioned, the port 228 provides improved visual access to componentson the transmission, such as the filter, and any indicator or “bypassbutton” thereon, indicating the operational status thereof. In otherwords, the indicator or button can be more easily viewed through filteraccess port 228 from more widely varied viewing positions than in theprior drip pan configuration.

Similarly, with respect to the prior art skirt and the new skirt 207,the prior skirt is identified in phantom lines at 240 in FIG. 9A. In oneembodiment of this invention, as described above, the new skirt 207 isexpanded outwardly as shown in the solid lines at this corner to form242. The smaller radius corner 242 corresponds to small radius corner221 of the pan 220, shown in FIG. 9. FIG. 9B graphically illustrates thecomparison of the new frame 215 and the respective orientations of theold skirt 26 designated 240 and the old prior art pan corner 245 (bothshown in phantom line).

With continued reference to FIG. 9B, in one embodiment, radius R₁ of theprior art pan corner 245 may be of greater length than the radius R₂ ofcorner 221 in the drip pan apparatus 200, thereby allowing the filteraccess port 228 to be moved more directly in line with a filter.However, even though the radius of corner 221 is smaller, as shown inFIG. 7, the o-ring seal 222 situated between the outwardly-facingperipheral surface 239 and the inwardly-facing peripheral surface 235unexpectedly seals the drip pan apparatus 200 and prevents egress offluids from access opening 205.

With reference now to FIGS. 9A, 10, and 11, in order for the frame 215to cooperate with the skirt 207 and form a small radius at the corner242 (shown in FIG. 7), the frame 215 may include an inner rim 218 and anouter rim 219 forming a trough 234 having a floor at 217 therebetween.Preferably, the rim 218 at corner structure 216 is at least partiallyexpanded outwardly from its position in the prior pan to accommodateskirt 207 and form the corner 242. Accordingly, trough 234 may vary inwidth “L” such that the width of corner structure 216 varies, asdescribed above, as required about frame 215 to accommodate the concavecurve 230 (shown in FIG. 7).

Furthermore, this corner structure at 216 will be appreciated bycontrasting prior art FIGS. 5 and 6 with new FIGS. 10 and 11. In FIGS.10 and 11, the frame 215 has been expanded at 217 to the length “L”. Inprior FIGS. 5 and 6, the frame was not so expanded. Thus, skirt 207 (atconcave curve 230) has been moved significantly to the left as viewed inFIGS. 10 and 11 as compared to the prior frame. According to embodimentsdisclosed herein, a filter F (FIG. 11) can advantageously be removed orinserted in a direction along and parallel to an elongated filter axis204 when the removable port cover 229 is removed from the pan 220.

If desired, in one embodiment, a trim ring (not shown) can be applied toaesthetically cover the frame 215, leaving only drip pan 220 and theports 223-226, 228 clear for use or for overall removal of the drip pan220 for access to the transmission 16.

Moreover, and if desired, while o-ring 222 is shown in a simple,outwardly facing, parallel sided groove, other groove shapes capturingthe o-ring 222 to the drip pan 220 (or alternatively to frame 215) maybe used. It will also be appreciated that the scale of the figures suchas in FIGS. 10 and 11 may be changed, such that o-ring 222 is actuallyin more of an oval or circular cross-section, or more of a squaredconfiguration than as shown in these figures, and more like, forexample, the cross-sectional configuration of peripheral seal 238 inFIGS. 10 and 11.

With reference to FIGS. 7 and 12, while the corners of the frame 215 andthe pan 220 are drawn and referenced as being defined by radii, oneskilled will appreciate that other shaped corners may be utilized. Evenso, the corner 221 and the corner 242 are cooperatively shaped. Theremaining corners of the pan 211-213 cooperate with their respectiveother corners (unlabeled) of the frame 215. The shape at the corner 221is, however, different than the shape of the corners at 211-213. Thus,the pan 220 may be inserted into the frame 215 in only one orientation.

The drip pan 220 otherwise performs the same sealing and accessfunctions for the “M” Model as in the prior BLACK HAWK® helicopterwithout requiring air frame modifications and without utilizing faceseals to seal any of the ports 223-226 and 228 or to form the sealbetween the drip pan 220 and the frame 215.

While the present invention has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, they are not intended to restrict or in any waylimit the scope of the appended claims to such detail. Additionaladvantages and modifications will readily appear to those skilled in theart. The invention in its broader aspects is therefore not limited tothe specific details and drawings shown and described. Accordingly,departures may be made from such details without departing from thescope of the general inventive concept.

1. A drip pan for cooperation with a frame secured to a depending skirt,which defines an access opening for access to a rotor transmission of ahelicopter, an oil filter being attached to the rotor transmission, theframe having an inwardly-facing peripheral surface, said drip pancomprising: a substantially planar member defining an access port andhaving an outwardly-facing peripheral surface, said access port forpermitting access to the oil filter, and said outwardly-facingperipheral surface defining a first pan corner and a plurality of othercorners, said outwardly-facing peripheral surface being adapted tocooperate with the inwardly-facing peripheral surface of the frame,wherein said first pan corner is asymmetric in curvature to said othercorners such that said substantially planar member is adapted to beremovably received within the frame in a single orientation.
 2. The drippan of claim 1 wherein said first pan corner is defined by a first pancorner radius and said other corners are each defined by a pan cornerradius that is larger than said first pan corner radius.
 3. The drip panof claim 1 wherein the inwardly-facing peripheral surface of the frameincludes a slot, said drip pan further including: at least one resilientmember secured to said substantially planar member and adapted toreleasably engage the slot.
 4. The drip pan of claim 1 wherein saidaccess port further includes an inwardly-facing groove and saidremovable port cover further includes a resilient member adapted toreleasably engage said inwardly-facing groove of said access port. 5.The drip pan of claim 1 further including a means for attaching saidremovable port cover to said substantially planar member.
 6. A drip panapparatus for a helicopter having an access opening defined by adepending skirt having at least two straight sides connected by acorner, wherein the corner is defined by an inwardly oriented concavecurve such that an extension of the concave curve intersects anextension of at least one straight side at an angle greater than zerodegrees, said drip pan apparatus comprising: a frame configured tocooperate with the skirt, including the inwardly oriented concave curve,said frame comprising: an inwardly-facing first frame corner defined bya first frame corner radius, and a plurality of other inwardly-facingframe corners each defined by a frame corner radius that is greater thansaid first frame corner radius.
 7. The drip pan apparatus as in claim 6further comprising: a drip pan for sealing cooperation with said frame,said drip pan comprising: a first pan corner defined by a first pancorner radius; and a plurality of other corners each defined by a pancorner radius that is greater than said first pan corner radius.
 8. Thedrip pan apparatus as in claim 7 wherein said first pan corner issealingly engageable with said first frame corner.
 9. The drip panapparatus as in claim 7 wherein said drip pan apparatus is for coveringan oil filter having a longitudinal axis; and wherein said drip pandefines an access port at said first pan corner, said access portorientated in a position to permit visual viewing of the oil filterthrough said port.
 10. The drip pan apparatus as in claim 7 wherein saiddrip pan has an outwardly-facing peripheral groove extending around saiddrip pan, including around said first pan corner, and said drip panapparatus further includes: an o-ring seal disposed in saidoutwardly-facing peripheral groove for sealingly engaging said frame.11. A drip pan apparatus for covering and sealing a helicoptertransmission access opening in a helicopter, the drip pan apparatuscomprising: a frame adapted to mount to the helicopter transmissionaccess opening, said frame having an inwardly-facing peripheral surfaceextending around said frame, said inwardly-facing peripheral surfacehaving a first frame corner defined by a first frame corner radius and aplurality of other frame corners each defined by a frame corner radiusthat is greater than said first frame corner radius; a drip pan havingan outwardly-facing peripheral surface extending around said drip pan,said outwardly-facing peripheral surface having a first pan cornerdefined by a first pan corner radius and a plurality of other drip pancorners each defined by a drip pan corner radius that is greater thansaid first pan corner radius, wherein said first pan corner cooperateswith said first frame corner and said drip pan is configured to beselectively affixed to said frame; and a seal member disposed betweensaid outwardly-facing peripheral surface and said inwardly-facingperipheral surface when said drip pan is affixed to said frame.
 12. Thedrip pan apparatus as in claim 11 wherein said drip pan defines anaccess port and the drip pan apparatus further comprises: an accesscover removably disposed within said access port.
 13. The drip panapparatus as in claim 12 wherein said access port is positioned in saiddrip pan to permit visual viewing of an oil filter through said accessport.
 14. The drip pan apparatus as in claim 12 wherein said accesscover has a viewing window to permit visual inspection of an oil filterwithout removal of said access cover.
 15. The drip pan apparatus as inclaim 12 wherein said access port has a groove formed in a peripheraledge thereof and said access cover further includes a resilient memberattached thereto to resiliently engage said groove and to detachablysecure said access cover to the access opening.
 16. The drip panapparatus as in claim 11 wherein said drip pan includes a drain holethrough which collected fluid may drain therethrough.
 17. The drip panapparatus as in claim 16 further comprising a drain tube attached tosaid drain hole.
 18. The drip pan apparatus as in claim 11 wherein thedrip pan further includes: a peripheral groove in said outwardly-facingperipheral surface, including around said first pan corner, and saido-ring seal is disposed within said peripheral groove.
 19. A drip panapparatus for covering and sealing an asymmetrical helicoptertransmission access opening defined by a depending skirt, the drip panapparatus comprising: a frame adapted to mount to the asymmetricalhelicopter transmission access opening, said frame comprising a firststraight side, a second straight side, and a corner structure connectingsaid first straight side and said second straight side, said firststraight side, said second straight side, and said corner structurecollectively defining an inwardly-facing peripheral surface, saidinwardly-facing peripheral surface having a first frame corner in saidcorner structure and a plurality of other frame corners, said cornerstructure having at least one width that is greater than the width ofsaid first straight side, said first frame corner defined by a firstframe corner shape, said other frame corners are each defined by a framecorner shape that is different than said first frame corner shape; adrip pan having an outwardly-facing peripheral surface extending aroundsaid drip pan, said outwardly-facing peripheral surface having a firstpan corner defined by a first pan corner shape and a plurality of otherdrip pan corners each defined by a drip pan corner shape that isdifferent than said first pan corner shape, wherein said first pancorner cooperates with said first frame corner and said drip pan isconfigured to be removably secured to said frame; and a seal memberdisposed between said inwardly-facing peripheral surface and saidoutwardly-facing peripheral surface.
 20. The drip pan apparatus of claim19 wherein said corner structure has at least one width that is greaterthan the width of said second straight side.
 21. The drip pan apparatusof claim 19 wherein said first frame corner is defined by a first framecorner radius and said other frame corners are each defined by a framecorner radius that is greater than said first frame corner radius; andsaid first pan corner is defined by a first pan corner radius and saidother pan corners are each defined by a pan corner radius that isgreater than said first pan corner radius.
 22. In combination: amultipassenger helicopter comprising: a flight deck; a cabin sectionrearwardly of said flight deck; a rotor transmission oriented at leastin part above said cabin section; and a transmission access openingwithin said cabin section for providing access to said rotortransmission; and a drip pan apparatus for covering said transmissionaccess opening, said drip pan apparatus comprising: a frame adapted tomount to said transmission access opening, said frame having aninwardly-facing peripheral surface extending around said frame, saidinwardly-facing peripheral surface having a first frame corner definedby a first frame corner shape and a plurality of other frame cornerseach defined by a frame corner shape that is different than said firstframe corner shape; a drip pan having an outwardly-facing peripheralsurface extending around said drip pan, said outwardly-facing peripheralsurface having a first pan corner defined by a first pan corner shapeand a plurality of other drip pan corners each defined by a drip pancorner shape that is different than said first pan corner shape, whereinsaid first pan corner cooperates with said first frame corner and saiddrip pan is configured to be selective affixed to said frame; and ano-ring seal disposed between said inwardly-facing peripheral surface andsaid outwardly-facing peripheral surface.
 23. The drip pan apparatus ofclaim 22 wherein said first frame corner is defined by a first framecorner radius and said other frame corners are each defined by a framecorner radius that is greater than said first frame corner radius, andsaid first pan corner is defined by a first pan corner radius and saidother pan corners are each defined by a pan corner radius that isgreater than said first pan corner radius.